Electrolytic means for treating metal



March 7, 1961 E. R. RAMIREZ ETAL ELECTROLYTIC MEANS FOR TREATING METALFiled Nov. 12. 1957 1NVENTOR$ [IQ/V57 K RAN/REE [R/KF BARK/7AM BY M mATTORNEYS ELECTROLYTIC MEANS FOR TREATING METAL Ernest R. Ramirez,Detroit, Mich., and Erik F. Barkman, Richmond, Va., assignors toReynolds Metals Company, Richmond, Va., a corporation of Delaware FiledNov. 12, 1957, Ser. No. 695,901

4 Claims. (Cl. 204-206) This invention relates to a novel apparatus andmethod for the electrolytic treatment of the edge portions of a flexiblemetal web, such as metal strip or foil. More particularly, the inventionconcerns an apparatus and method for the edge anodizing of aluminumstrip or foil in thin gages.

In many industrial applications in which metal strip or foil is used, itbecomes necessary to subject the edge portions to special types ofelectrolytic pretreatments or after-treatments. Examples of suchelectrolytic treatments include the removal of burrs, protuberances, andslivers from the edges of metal webs which have been produced byslitting or shearing, as well as edge electroplating operations in themanufacture of blanks for can bodies. Where the metal in question isaluminum strip or foil, which is to be used, for example, in electricalwindings for transformers or other electrical devices, the removal ofburrs and protuberances is a necessity in order to avoid subsequentshort circuits, punctures, and the like when the aluminum is convertedinto electrical windings. Moreover, for certain types of applications,it is desirable that an oxide coating be established over the surfacesof the aluminum strip or foil, and in such cases, it is highly desirablethat a localized precoat of oxide along the edges of the material befirst produced along the edges of the aluminum, to be followedthereafter by overall anodizing. The production of such a precoat ofoxide by a type of edge anodizing is described in our copendingapplication Serial No. 688,669, filed October 7, 1957.

Up to the present time, there has not been available any type ofequipment which would permit electrolytic edge treatment of metal stripor foil by other than unsatisfactory and time consuming batch methods.Thus, apparatus is known for continuous over-all plating or etching ofmetal webs, but no practical means is disclosed in the prior art forconfining the action of the treating baths to the edge portions.

In connection with the preparation of can blanks, for example, apparatusis known for immersing edge portions of back plate in a series ofsuccessive treating baths, but this apparatus and method is notadaptable to either batch or continuous operation with long webs ofmetal, particularly of metal in thin gages.

Similarly, mechanical methods of removing edge burrs and protuberancesin the case of aluminum strip are unsatisfactory when dealing with thingages such as those in the range of 0.004" to 0.008".

In accordance with the present invention, there is provided an apparatusor device for either continuous or batch electrolytic treatment of metalstrip or foil which is adaptable for edge conditioning, edge plating,edge anodizing, or similar types of treatments in which the electrolyticaction is confined to the edges of the metal, leaving the central areasunaffected.

In the apparatus of this invention means are provided for passing aflexible web of metal strip or foil, which itself constitutes anelectrode, through an-electro- States Patent lytic bath contained withina chamber provided with another electrode or set of electrodes disposedopposite the edge or edges to be treated, and having sets of perviousresilient material, in contact with said metal web so as to seal oil thecentral portions of the metal and to prevent access of the bath thereto.

In accordance with the present invention there is also provided a novelmethod for the continuous edge electrolytic treatment of flexiblemetallic webs, such as strip or foil, whereby the treating electrolyteis permitted to come into contact only with the edges of the metal andareas immediately contiguous thereto. The method is illustrated byexamples of the edge conditioning and edge anodizing of aluminum stripor foil in thin gages, but in its broader aspects it is applicable tosimilar operations and on other metals.

For a better understanding of the invention and its purposes,advantages, and details, reference is now made to the present preferredembodiment of the invention which is shown, for purposes of illustrationonly, in the accompanying drawing.

In the drawing:

Fig. l is a perspective view of the exterior of the elec-' trolytictreatment apparatus;

Fig. 2 is a view in cross section along the line A-A of Fig. l of theelectrolytic treatment apparatus.

The component parts of the preferred embodiment of the electrolytictreatment apparatus comprising the present invention may be comprised ofvarious kinds of materials, provided that these materials are resistantto the action of the chemicals used in the electrolytic bath.Hereinafter, the apparatus will be described in connection with the edgeconditioning or edge anodizing of a web of aluminum metal of thin gage,although it is to be understood that the device may be utilized forother purposes where it is desired to apply electrolytic treatment toone or both edges of a flexible metal strip or foil.

As shown more particularly in Figs. 1 and 2 of the drawing, theapparatus comprises a vessel 10 com prising matching upper portion 12and lower portion 14. When the upper and lower portions are joinedtogether by suitable fastening means 16, such as bolts, there is formedchambers 18 which serve as containers for the electrolytic bath whichnormally fills said chambers nearly to the top.

made of any suitable material, depending upon the pun pose for which thedevice is to be utilized, and which" will be immersed in the electrolyteduring its opera: tion. Conductors 22 passing through openings 24 serveto supplyv electric current to the electrodes 20, from a power sourcenot shown, said conductors being con nected to the electrodes. In theform of device shownin the drawing, a set of electrodes is depicted, aswell as a dual chamber, but it will be understood that if desired, theapparatus may he so constructed, for example, in order to treat but oneedge of the metal, that only-a single electrode, or a single electrodeand a single edge of the metal are contained within a treating chamber.

The flexible metal web 26 to be treated is advanta; geously suppliedfrom a roll 28, suitably mounted on .a shaft or spindle feeding meansshown generally at 3t0, Since the metal web is to form the otherelectrode, acpn ductor is suitably connected thereto for example bybrush or sliding contact to supplylcurrent from a power, source and tocomplete the circuit. The metal web 25 hotli enters and leaves theapparatus through narrow slotted portions 34, one of which is shown atthe exit end in Fig. 2, but for which a corresponding entrance slottedportion is provided, but not shown, in the opposite or entrance end ofthe apparatus. Metal web 26 may than be rewound, or passed as such to asubsequent processing stage.

In the embodiment shown in Fig. 2, both the upper and lower portions ofthe electrolysis vessel are provided with metal web guiding meanscomprising a pair of opposed centrally disposed ribs 36 terminating infiat faces 38. The flat faces 38 are in juxtaposition and spaced apartto permit passage of the metal web between the faces. Supported in eachrib 36 is a pair of sealing members 40, which extend outward from thefaces 38 to contact the metal web 26, sealing off the central portion ofthe web, and leaving the edge portions 42 exposed to the action of theelectrolyte. The sealing members 40 extend longitudinally of the web,and they may be made of any suitable impervious resilient material, suchas natural or synthetic rubber, plastic materials, and the like.

Electrolyte is supplied to the treating vessel by means of supply pipe44 and removed through discharge pipe 46. Where circulation ofelectrolyte is to be maintained, for example, electrolyte fluid issupplied by suitable means such as a pump, shown generally at P.

The electrodes 20 extend longitudinally of the treatment vessel and arespaced apart from and opposite to, and extend along the line of themetal edges 42 which are to be treated. Where edge conditioning oranodizing of aluminum is to be carried out, for example, the electrodes20 will serve as cathodes and may be made of graphite, lead, or othersuitable material.

The mode of operation of the apparatus of the preferred embodiment ofthis invention comprises passing the metal web to be electrolyticallytreated from the roll 28 into the treatment vessel 10 which ismaintained substantially filled with electrolyte, through entrance slot34 and between sealing members 40. The metal web passes through theelectrolyte treating chambers 18 with the edges 42 immersed in theliquid and the central area of the web sealed off from access of theelectrolyte, the web emerging at the exit slot 34. The speed of the webis regulated as desired in accordance with the type of operation beingcarried on. An electric current, which may be either alternating ordirect, is passed through the bath via electrodes 20 and the metal web.If circulation of the electrolyte is required, it is maintained by meansof pump P. Operation may be either batch or continuous, in the lattercase by changing rolls of metal web to afford an uninterrupted supply ofmetal, and by circulating fresh electrolyte into the treating chamber.

The novel continuous method for the electrolytic edge treatment of metalwebs which also forms a part of this invention may be illustrated withreference to the treatmerit of aluminum strip or foil in thin gages, aspreviously defined. Our novel method for electrolytic edge treatmentcomprises continuously passing a web of metal in a horizontal positionthrough an electrolytic treating bath with the edges of the web immersedin said bath, and the remainder of the Web maintained out of contactwith said bath. In the case of aluminum, such as thin gage aluminum, thebath is an anodizing solution such as sulfuric acid, the aluminum ismade the anode, and the cathode is graphite or lead.

Thus, in edge conditioning of aluminum strip or foil, burs orprotuberances may be removed by using as the electrolyte a hot sulfuricacid solution of from about 10 to percent strength by weight, preferablyabout 15%. A temperature of between about 100 and 130 F., preferablyabout 120 F. has been found to give satisfactory results. The currentdensity on the exposed edge portions of the aluminum is maintained atabout 1,000 to 5,000 amperes per square foot, while that on the cathodeis generally about one-tenth of that used on the metal edges. Bymaintaining the metal web with its edges below the surface of thesulfuric acid bath, while at the same time masking the central portionsby suitable means such as; resilient dam in contact longitudinally withand near the edges of the strip, the acid is prevented from attackingthe central portions of the web. Rounded edges are obtained which aresuitable for subsequent edge anodiz- Anodizing of the edge portions ofaluminum may be performed in essentially the same manner as edgeconditioning, except that the temperature of the sulfuric acid bath willgenerally be kept in the vicinity of to 80 F. to permit establishment ofan oxide coating the edges of the metal. Such anodizing may follow theedge conditioning, or may be carried on as a separate originaloperation.

While we have illustrated and described the present preferredembodiments of the invention, it will be recognized that the inventionmay be otherwise variously embodied and practiced within the scope ofthe following claims.

We claim:

1. Apparatus for the electrolytic treatment of the edge portions of aflexible metal web comprising a hollow vessel for containingelectrolyte, means for supplying electrolyte to and removing it fromsaid vessel, means.

for guiding said metal web through the electrolyte comprising a pair ofopposing ribs terminating in flat faces spaced apart to permit passageof the metal web between them, stationary resilient sealing meansmounted in said ribs extending toward and longitudinally of said metalweb and adapted to maintain contact with the metal web near the edgeportions thereof to confine the action of the electrolyte to said edgeportions, and at least one electrode mounted in the interior of saidvessel opposite the line of passage of said metal web, and means forconducting electric current to said electrode and to the metal web.

2. Apparatus for the electrolytic treatment of the edge portions of aflexible metal web comprising a hollow vessel for containingelectrolyte, means for circulating electrolyte through said vessel,means for guiding the metal web through the electrolyte comprising apair of opposing ribs centrally disposed in said vessel and mountedrespectively on the upper and lower walls thereof and terminating infiat faces spaced apart to permit passage of the metal web between them,a pair of opposed stationary resilient sealing members mounted in saidribs extending toward and longitudinally of said metal web and' adaptedto maintain contact with the metal web near the edge portions thereof toconfine the action of the electrolyte to said edge portions, a set ofelectrodes mounted in the interior of the vessel and opposite the lineof passage of said metal web, and means for conducting an electriccurrent to said electrodes and to the metal web.

3. Apparatus for the electrolytic treatment of the edge portions of aflexible metal web comprising a hollow vessel for containingelectrolyte, means for circulating electrolyte through said vessel,means for guiding the metal web through the electrolyte so that its edgeportions are immersed therein while the central area of the web remainsdry comprising a pair of opposed ribs centrally disposed in said vesselalong the line of passage of the web and mounted respectively on theupper and lower vessel walls and terminating in fiat faces spaced apartto permit passage of the metal web between them, and pairs of stationaryopposed resilient sealing members mounted in and on opposite portions ofthe faces of said ribs and extending between opposite walls of thevessel and toward and longitudinally of said metal web and adapted tomaintain sealing contact with the metal web near the edge portionsthereof to confine the action of the electrolyte to said edge portions,21 set of electrodes mounted in the interior of said vessel and oppositethe line of passage of the edge portions of said metal web, and meansfor conducting an electric current to said electrodes and to the metalweb.

Y 4. Apparatus for the electrolytic treatment of the edge portions of'aflexible metal webgcomprising a'hollow vessel for containingelectrolyte, means for circulating electrolyte through said vessel,means for feeding the metal web to said vessel, a pair of entrance andexit slots for the web in the opposite walls of the vessel, means forguiding the metal web through the electrolyte comprising a pair ofopposing ribs centrally disposed in said vessel and forming extensionsof the upper and lower walls thereof and terminating in flat facesspaced apart to permit passage of the web between them, pairs ofstationary opposed resilient sealing members mounted in and on oppositeportions of the faces of said ribs and extending toward andlongitudinally of said metal web and adapted to maintain contact withsaid metal Web near the edge portions thereof to confine the action ofthe electrolyte to said edge portions, flat electrodes mounted in theinterior of said vessel parallel to and opposite the line of passage ofsaid metal web, and means I for conducting an electric current to saidelectrodes and to the metal web.

References Cited in the file of this patent UNITED STATES PATENTS2,052,962 Booe Sept. 1, 1936 2,174,071 Grupe Sept. 26, 1939 2,225,778Hellman Dec. 24, 1940 2,607,724 Laing Aug. 19, 1952 2,694,040 Davis etal Nov. 9, 1954 2,695,269 De Witz et a1 Nov. 23, 1954 2,699,421 NieterJan. 11, 1955 2,764,542 Pullen Sept. 25, 1956 Harrison June 21 1932 i

1. APPARATUS FOR THE ELECTROLYTIC TREATMENT OF THE EDGE PORTIONS OF AFLEXIBLE METAL WEB COMPRISING A HOLLOW VESSEL FOR CONTAININGELECTROLYTE, MEANS FOR SUPPLYING ELECTROLYTE TO AND REMOVING IT FROMSAID VESSEL, MEANS FOR GUIDING SAID METAL WEB THROUGH THE ELECTROLYTECOMPRISING A PAIR OF OPPOSING RIBS TERMINATING IN FLAT FACES SPACEDAPART TO PERMIT PASSAGE OF THE METAL WEB BETWEEN THEM, STATIONARYRESILIENT SEALING MEANS MOUNTED IN SAID RIBS EXTENDING TOWARD ANDLONGITUDINALLY OF SAID METAL WEB AND ADAPTED TO MAINTAIN CONTACT WITHTHE METAL WEB NEAR THE EDGE PORTIONS THEREOF TO CONFINE THE ACTION OFTHE ELECTROLYTE TO SAID EDGE PORTIONS, AND AT LEAST ONE ELECTRODEMOUNTED IN THE INTERIOR OF SAID VESSEL OPPOSITE THE LINE OF PASSAGE OFSAID METAL WEB, AND MEANS FOR CONDUCING ELECTRIC CURRENT TO SAIDELECTRODE AND TO THE METAL WEB.